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Database architecture

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This page is in active development, some content may be inaccurate.

Model​

At a high level the database model can be described in the image bellow.

high level diagram

Important things to note about the relationship:

  • An environment exists within a given namespace and always has a current build
  • A build belongs to a particular environment and has associated condapackage and buildartfacts
  • A buildartifact is a way for the database to keep track of external resources for example s3 artifacts, filesystem directories, etc
  • A condapackage is a representation of a given Conda package which belongs to a given condachannel
  • A specification is the environment.yaml using in conda env create -f <environment.yaml>

The following will generate the database model shown bellow. It was generated from the examples/docker example. You'll see in the command that we are excluding several tables. These tables are managed by celery.

pip install eralchemy  # not available on conda-forge
eralchemy -i "postgresql+psycopg2://admin:password@localhost:5432/conda-store"  \
    -x celery_tasksetmeta celery_taskmeta kombu_queue kombu_message alembic_version \
    -o output.png

entity relationship diagram

Migrations​

conda-store relies on SQLAlchemy for ORM mapping, and on Alembic for DB migrations.

The procedure to modify the database is the following :

  • First, modify the ORM Model according to the changes you want to make
  • edit the file conda-store-server/alembic.ini and replace the value for entry sqlalchemy.url to match the connection URL of your database.

For example (when postgres was started via docker-compose):

script_location = alembic
sqlalchemy.url = postgresql+psycopg2://postgres:password@localhost:5432/conda-store
  • in your command line, run the following :
cd conda-store-server/conda_store_server
alembic revision --autogenerate -m "description of your changes"

  • You should have a new file in conda-store-server/conda_store_server/alembic/versions/ . Review it thoroughly. It contains the alembic operations (op) to actually modify the database, either when upgrading (upgrade function) or downgrading (downgrade)

  • You can migrate your data within these upgrade/downgrade functions, for example :

from alembic import op

# revision identifiers, used by Alembic.
revision = 'abcdef01234567'
down_revision = '987654321f0edc'
branch_labels = None
depends_on = None

def upgrade():

    # operations to modify the database structure
    # ...
    op.create_table(
        'new_table',
        Column('id', INTEGER, primary_key=True),
        Column('field1', VARCHAR(50), nullable=False),
        Column('field2', INTEGER),
        Column('timestamp', TIMESTAMP, server_default=func.now())
    )
    # ...

    op.execute('''INSERT INTO new_table (field1, field2)
                  SELECT field1, field2
                  FROM old_table''')

    # other operations to modify the database structure
    # ...


def downgrade():

    op.drop_table('new_table')

  • Once you're sure about the changes generated, you can apply them by running :
alembic upgrade head